Briton Robson, 18, was a set and a break up when the 20-year-old Spaniard pulled out.
Robson, up to world number 74 after reaching the fourth round of the US Open, will face one of China’s Jie Zheng or Taiwan’s Yung-Jan Chan in the second round.
She is Britain's top-ranked player, one spot ahead of Heather Watson in the WTA list, with both youngsters looking to maintain and hopefully improve their rankings ahead of the Australian Open in January.
In other first-round matches Bojana Jovanovski of Serbia beat Timea Babos of Hungary 6-1 6-3, while fifth seed Chanelle Scheepers of South Africa beat Wang Qiang of China 6-0 6-3.
Mandy Minella of Luxembourg also beat Pauline Parmentier of France 7-5 3-6 6-3.